the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Brief communication: How deep is the snow at the Mount Everest?
Wei Yang
Huabiao Zhao
Baiqing Xu
Jiule Li
Weicai Wang
Guangjian Wu
Zhongyan Wang
Tandong Yao
Abstract. Exploring the snow thickness at the Mount Everest has long been a topic of interest for studying geodesy, cryosphere and climate change, but has not yet been measured successfully. Here, we report the ground-penetrating radar survey of snow thickness along the northern slope of the Mount Everest in May 2022. Our radar measurements display a gradual increasing transition of snow thickness along the north slope, and the mean snow thickness estimates at the Mount Everest is approximately 9.5 m. This updated snow thickness at the Mount Everest is much deeper than previously reported values (0.9~3.5 m).
Wei Yang et al.
Status: open (until 04 Apr 2023)
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RC1: 'Comment on tc-2022-268', Anonymous Referee #1, 10 Mar 2023
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The authors present a unique dataset - a geophysical survey acquired on the north ridge of Mount Everest, that shows snow depth with distance from the peak. It provides more detailed observations than are otherwise available, and suggests overall that the snow/firn is deeper than previously thought. I am not entirely convinced that these measurements are critical for studies of the cryosphere and climate change (line 25), but they are certainly of broad interest and provide a small window into one of the most inaccessible places on our planet, and for that main reason I'd be pleased to see them published. However, before they are, I would suggest some revisions are required in the way the manuscript is presented:
- the paragraph starting line 26 provides a critical assessment of previous attempts to measure snow depth at the summit, but I can't find any suggestion in the cited papers that there were major doubts in the measurement. I can easily imagine that there is great variability in snow depth depending on exactly where you acquire it from, and at what time of the season you take the measurement. I suggest the authors repackage the paragraph as being a summary of previous work rather than those previous attempts not being successful?
- Related to this, I'd be interested to hear the authors view on whether the timing (season) of the survey makes much of a difference to the snow depth at the summit. Might these results differ if acquired in the post-monsoon, or can we consider them to be consistent throughout the year? I think this is needed to put this snapshot into some sort of broader (longer) context - and very pertinent as the authors themselves state the temporal variability is significant (line 18). A couple of lines added to Section 3 would be good to see in this regard.
- I have never had the priviledge of summitting Mount Everest, but it looks to me from the photograph in Figure 1 that there is exposed bedrock very close to the surface at the summit location. According to the annotation, the survey profile passes almost directly over that exposed bedrock, but there is no evidence of it in the radargram. I'd be keen for the authors to provide some explanation for this.
- The data presented here are along one survey line, chosen (presumably) to coincide with the established climbing route. I would like to see some acknowledgement that moving the profile several metres either side (even though this might not be safe in practice) could yield very different results. The way the data are presented at the moment is as if these measurements represent snow depth across the whole of the north ridge.
- Related to that, since the exact location of the geophyical survey is critical to the data that are retrieved, I'd like to see some precise co-ordinates added to the manuscript (maybe as graticules on Figure 1b) so that anyone wishing to repeat the survey in the future can do so with confidence.A few additional minor points:
- it would be normal to simply use the term 'Mount Everest' rather than 'the Mount Everest'.
- given how critical the transmission velocity is in determining the thickness, I suggest adding an uncertainty range to each of the stated values (based on a min of 0.2 m/ns and a max of 0.27 m/ns).
- I struggle to make out the red line on Figure 1c - experiment with some different (lighter?) colours?Citation: https://doi.org/10.5194/tc-2022-268-RC1 -
RC2: 'Comment on tc-2022-268', Anonymous Referee #2, 10 Mar 2023
reply
TC-2022-268 is a timely and important contribution to quantify the snow depth on the north side of the Mount Everest summit. I congratulate the authors and the entire expedition team on a herculean effort to obtain such valuable data in exceptionally challenging conditions. Although the manuscript represents an important contribution to the cryosphere and broader geophysical communities, there are a number of issues referenced below that need to be addressed prior to eventual publication.
- More background is needed in the Introduction about the significance of summit snow depth in the context of climate variability and change. The geodesy discussion is relevant but perhaps a bit tangential to the climate change and cryosphere connection. Also, additional discussion about why/how the summit snow depth is an important indicator of the cryosphere response to climate change would be helpful. This could be done in the context of the Potocki et al. (2022) and Brun et al. (2022) articles which are already cited. I also recommend limiting citations to peer-reviewed scientific articles as much as possible.
- A bit more discussion about the hypothesized physical processes responsible for the seasonal and inter-annual variability of summit snow depth could be helpful. Do the authors suggest that the snow accumulation is the result of snowfall (precipitation) or primarily deposition (snow drift) from snow blowing up from lower slopes? How much ablation can be expected due to sublimation? Is there any evidence of melt in the GPR data, which both Matthews et al. (2020) and Potocki et al. (2022) suggest may now occur even at the summit?
- Do the GPR data provide any indication of whether some of the summit snow depth could be the result of rime ice accretion during the monsoon, similar to what occurs in Patagonia? See: Whiteman, C. D., and R. Garibotti, 2013: Rime Mushrooms on Mountains: Description, Formation, and Impacts on Mountaineering. Bull. Amer. Meteor. Soc., 94, 1319–1327, https://doi.org/10.1175/BAMS-D-12-00167.1.
- Is a different photo available for Figure 1a? Are the darker colors below the summit old prayer flags, lower albedo snow, or rock? It is very hard to tell in this photo but I suppose old prayer flags? An improved photo could help this interpretation as the darker colors could easily be mistaken for rock?
- The authors reference the importance of future snow core drilling and repeated GPR measurements. Are there any lessons learned from the 2022 expedition and/or suggestions for future expeditions/researchers? Additionally, are you able to offer testable hypotheses for future researchers?
- I suggest using either snow thickness, snow depth, or snow height and being consistent instead of using multiple terms to refer to the same thing which may confuse the reader. Snow depth is perhaps a more commonly used term?
- I suggest consistent use of Mount Everest vs. Mount Chomolungma throughout.
- Are there GPS height measurements for the rock indicated by the blue star in Figures 1a and 1b?
- Can contour lines and the international border be added to the map in Figure 1b?
Minor Comments
Line 7: “the” preceding Mount Everest not needed here or elsewhere
Line 17: citation needed for China and Nepal height declaration
Line 18: considerable inter-annual variability in the snow thickness may also exist?
Line 21: suggest changing “In additions,” to “In addition,”
Line 23: suggest changing “extreme high elevation” to “extreme high elevations”
Line 24: suggest changing “the state of snow at the Mount Everest are critical” to “snow depth at the Mount Everest summit is critical”
Line 49: remove “t” after “Mount Everest t.”
Lines 53-54: What were the snow properties at 6500 m and 7028 m in 2005 and how certain are you that these properties are representative of the summit snow in 2022?
Line 55: suggest changing “processing package by apply a frequency” to “processing package by applying a frequency”
Line 69: space needed after “velocity.”
Line 81: suggest changing “was compacted for producing high snow density.” to “was compacted resulting in high snow density.”
Line 82: suggest changing snow density to kg m-3
Line 85: suggest changing “In addition to reveal the” to “In addition to revealing the”
Line 87: suggest deleting “was” between “reflection layer was existed”
Line 88: suggest changing “maybe” to “may be”
Lines 92-93: suggest adding “the” between “of snowpack” and deleting “in the world”
Lines 96-97: incomplete sentence starting “It is worth noting . . .” and therefore suggest revising
Line 98: suggest changing “at the Mount Everest is also necessary” to “at Mount Everest are also necessary”
Line 99: suggest deleting “favor” and “source”
Citation: https://doi.org/10.5194/tc-2022-268-RC2
Wei Yang et al.
Wei Yang et al.
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